This invention relates to methods for minimizing consequences of accidents in motor vehicles and to control arrangements for practicing such methods.
There are conventional systems for vehicles that assist the vehicle operator in critical situations to prevent an impending accident in so far as possible by optimal braking or at least reducing the impact velocity at the point of collision to a minimum. Such automatic braking systems are included in many vehicles under the general designation ABS. The basic function of an ABS is to prevent locking of the vehicle wheels upon emergency braking so that the steerability of the vehicle can be preserved even in fill braking. This gives the vehicle operator the opportunity to circumvent the point of collision even in full braking, thereby avoiding a collision, provided there is not an unavoidable accident situation in which no evasion whatever is physically possible.
There are conventional systems intended to prevent a collision of the vehicle with an obstacle by producing a controlled acceleration or deceleration and/or by evasive maneuvers. Such systems, referred to briefly as CAS (xe2x80x9ccollision avoidance systemsxe2x80x9d), are intended to guide a vehicle out of collision situations which have been recognized by sensors so that a collision is avoided by an automatic steering arrangement disconnected from the operator, and therefore by steering maneuvers which must be performed independently of the operator, as well as automatic accelerations and decelerations of the vehicle controlled independently of the operator. U.S. Pat. No. 5,541,590 discloses an arrangement that evaluates the surroundings of a vehicle for possible collisions by evaluating images of the surroundings, taken by a running CCD camera and, with reference to additional signals relating to the operating condition of the vehicle, exerts an influence on vehicle speed and steering movement. In another arrangement, described in U.S. Pat. No. 5,461,351, the roadway area to be monitored is segmented and, with incorporation of vehicle condition data, rules are derived on how a detected obstacle can be avoided by braking and steering maneuvers. The chief problem of these prior art arrangements is their complexity, requiring an expenditure which is not practical. Moreover, accident situations may arise so suddenly that avoidance of the accident by early evasion is no longer possible.
European Patent Publication No. 0 545 437 discloses a method of avoiding collisions of motor vehicles by which other vehicles at a distance in the direction of travel are detected and warning messages warn the vehicle operator of impermissible approaches to such vehicles. Then, since the minimum spacing from the vehicles has not yet been attained, the operator has an opportunity to initiate appropriate braking maneuvers. When the spacing falls below a minimum allowable distance, the vehicle is braked automatically so that the required safe interval is restored. In an accident situation that rises suddenly, this system carries out an automatic emergency braking for optimal velocity reduction.
German Offenlegungsschrift No. 38 30 790 also discloses a method and an arrangement for automatic collision avoidance of automatically guidable vehicles, which recognizes current collision hazards using sensors. If a collision hazard is ascertained, the system guides the vehicle along a collision-free path around a detected obstacle. If an unavoidable accident situation produces an impending collision, however, this system involves the danger that the automatically guided vehicle may be directed from a more favorable collision position into a collision position less favorable to the occupants.
German Offenlegungsschrift No. 196 47 283 discloses an arrangement for avoidance and/or minimization of conflict situations in road traffic which is capable of controlling the operation of a vehicle in an unavoidable accident situation. If the operator is no longer in a position to avoid an impending accident, this arrangement intervenes and takes steps to limit damage, for example, by preferring a collision with a garbage can on the sidewalk to hitting a person in the roadway. Thus, this arrangement performs an automatic steering function, requiring a correspondingly high technical expense.
Accordingly, it is an object of the present invention to provide a method and control arrangement for minimizing the consequences of accidents which avoids disadvantages of the prior art.
Another object of the invention is to provide a method of minimizing the consequences of accidents in the event of an unavoidable collision which requires the least possible technical expenditure.
These and other objects of the invention are attained by providing a method and arrangement for braking of the individual vehicle wheels and/or an influence on the vehicle steering system in such a way that the vehicle is rotated into a position which minimizes the consequences of accident. In this way, a critical angle of impact or an unfavorable xe2x80x9coffsetxe2x80x9d impact for the occupants of the vehicle can be avoided.
An evaluating unit in accordance with the invention may take into consideration certain vehicle-specific features and the dynamic data involved in the accident situation in such a way that a reduction of the consequences of accident is achieved.
In a particular embodiment of the invention, the distance or the continually varying relative coordinates between the vehicle and an obstacle are determined, and the rate of change of the distance or of the relative coordinates is used to control a braking maneuver. In this way, the evaluating unit can recognize whether there is an unavoidable accident situation and what characteristics the accident situation presents. Moreover, numerous different accident situations, each with an associated preferred angle of impact, may be stored in a memory so that the evaluating unit can transmit the required control signals to an automatic braking system and/or a steering control system to rotate the vehicle, for example, in the direction of the desired angle of impact.
An unavoidable accident situation occurs when an avoidance or a stop short of the obstacle is no longer possible. This is recognized by the evaluating unit from the limit values stored in a memory. If these limit values are transgressed, the evaluating unit initiates an automatic braking maneuver to obtain as low an impact energy and as optimal a vehicle orientation at impact as possible. In fact, it may definitely be expedient to permit a somewhat higher impact velocity, if appropriate braking maneuvers can achieve a more favorable impact position for the vehicle. The criteria for this decision are preferably stored in a memory to which the evaluating unit has constant access.
It may be advantageous to control the braking maneuver as a function of seat occupancy. If there are no occupants in the vehicle other than the driver, a different angle of impact may be favorable for purposes of reducing the consequences of accident to the driver than would be the case if the vehicle were fully occupied.
The method may be carried out in such a way that, in an unavoidable accident situation, a maximal deceleration of vehicle speed occurs before a correction of the angle or position of impact is undertaken. Whether such a two-step braking maneuver is to be employed may be made dependent on the particular accident situation encountered.
To practice the method according to the invention, a control arrangement may be provided which includes an evaluating unit receiving environmental data from environmental sensors attached to the vehicle and receiving internal vehicle data from the vehicle electronics unit and which can recognize an unavoidable accident situation based on these data and initiate individual braking of the several vehicle wheels in such a manner that the vehicle tends to assume a preassigned, optimal impact position.
In this regard, a favorably chosen angle of impact can help minimize the consequences of a collision. If, for example, the environmental sensors recognize an impending laterally offset frontal impact, unilateral braking of the wheels may accomplish a change in the angular position of the vehicle to achieve better utilization of the areas of impact energy-absorbing deformation which are built into the vehicle.
In a preferred embodiment, the control arrangement includes a memory containing vehicle-specific features and limit values that are continually compared with the environmental data and vehicle data in the evaluating unit and are utilized to control the braking maneuvers in an accident situation. For different vehicle types, correspondingly different characteristic features may be stored in the memory so that a reduction of the consequences of accident can be optimally achieved, even for different vehicles, without great technical expenditure. The memory may contain the characteristic features of a plurality of possible accident situations, each with appropriate optimal angles of impact, where the desired angles of impact will as a rule have different values for different vehicle types.
In a preferred control arrangement, the evaluating unit controls the braking of the individual wheels by a brake control that is part of an automatic braking system. Hence, an automatic brake system, which is present in the vehicle in any event, may be utilized so that the additional technical expenditure to provide the method and arrangement according to the invention can be kept quite small. In an accident situation, the evaluating unit takes control of the automatic braking system, whereas otherwise the automatic braking system is operated in the conventional manner.
Further objects and advantages of the invention will be apparent from a reading of the following description in conjunction with the accompanying drawing which is a schematic block diagram illustrating a representative embodiment of a control arrangement in accordance with the invention.